Adding tests and minor code changes to ensure that we properly handle the distinction between bytes and text when dehydrating/rehydrating messages.

django_mailbox/tests/messages/generic_message.eml

@@ -7,8 +7,7 @@ Message-ID: <CAMdmm+hGH8Dgn-_0xnXJCd=PhyNAiouOYm5zFP0z-foqTO60zA@mail.gmail.com>
 Subject: Message Without Attachment
 From: Adam Coddington <test@adamcoddington.net>
 To: Adam Coddington <test@adamcoddington.net>
-Content-Type: text/plain;
-	charset="iso-8859-1"
+Content-Type: text/plain; charset="iso-8859-1"
 Content-Transfer-Encoding: 7bit
 
 Hello there.

django_mailbox/tests/messages/message_with_invalid_content_for_declared_encoding.eml

@@ -0,0 +1,9 @@
+Date: Fri, 30 Jan 2012 11:30:01 PST
+Subject: Tjest
+From: "Somebody" <somebody@somewhere.com>
+To: idontknow@somewhere.com
+MIME-Version: 1.0
+Content-Type: text/plain; charset="us-ascii"
+Content-Transfer-Encoding: 7bit
+
+Ýòî ñîîáùåíèå èìååò íåïðàâèëüíóþ êîäèðîâêà.

django_mailbox/tests/messages/message_with_invalid_payload_encoding.eml

@@ -0,0 +1,9 @@
+Date: Fri, 30 Jan 2012 11:30:01 PST
+Subject: Tjest
+From: "Somebody" <somebody@somewhere.com>
+To: idontknow@somewhere.com
+MIME-Version: 1.0
+Content-Type: text/plain; charset="raspberries"
+Content-Transfer-Encoding: 7bit
+
+Это сообщение имеет неверная кодировка.

django_mailbox/tests/test_process_email.py

@@ -131,3 +131,61 @@ class TestProcessEmail(EmailMessageTestCase):
             expected_text,
             actual_text,
         )
+
+    def test_message_with_unknown_charset(self):
+        """ Ensure that we gracefully fail at handling unknown encodings.
+
+        Should an unknown encoding be used, we should:
+
+        - Add a X-Django-Mailbox-Altered-Message header
+        - Use UTF-8 (with replacement) as the de-facto (and probably incorrect)
+          encoding for this payload part.
+
+        """
+        email_object = self._get_email_object(
+            'message_with_invalid_payload_encoding.eml'
+        )
+
+        msg = self.mailbox.process_incoming_message(email_object)
+
+        actual_body = msg.get_text_body()
+
+        expected_body = (
+            u'\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd '
+            u'\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd'
+            u'\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd '
+            u'\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd '
+            u'\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd'
+            u'\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd '
+            u'\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd'
+            u'\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd.'
+        )
+
+        self.assertEqual(
+            expected_body,
+            actual_body,
+        )
+
+    def test_message_with_invalid_content_for_declared_encoding(self):
+        """ Ensure that we gracefully handle mis-encoded bodies.
+
+        Should a payload body be misencoded, we should:
+
+        - Decode the message (with replacement) using the declared encoding.
+        - Always return a payload body in the declared encoding, using python's
+          usual replacement mechanisms.
+
+        """
+        email_object = self._get_email_object(
+            'message_with_invalid_content_for_declared_encoding.eml',
+        )
+
+        msg = self.mailbox.process_incoming_message(email_object)
+
+        actual_body = msg.get_text_body()
+        expected_body = '??? ????????? ????? ???????????? ?????????.'
+
+        self.assertEqual(
+            actual_body,
+            expected_body,
+        )